Systems and methods for optimizing emissions from simultaneous activation of electrosurgery generators

ABSTRACT

A method for optimizing emissions from simultaneous activation of electrosurgery generators is presented including delivering first energy to a first target tissue via a first energy module, the first energy represented as a first waveform having a first phase, delivering second energy to a second target tissue via a second energy module, the second energy represented as a second waveform having a second phase, applying the first energy in a first energy mode, and applying the second energy in a second energy mode. The method further includes the steps of comparing the first phase of the first energy waveform with the second phase of the second energy waveform and adjusting a relative phase between the first and second energy waveforms based on the comparison step.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of, and priority to, U.S.Provisional Patent Application Nos. 61/975,101, 61/975,120, and61/975,126, all of which were filed on Apr. 4, 2014. This application isrelated to U.S. patent application Ser. Nos. 14/592,026, and 14/592,046,all of which were filed on Jan. 8, 2015. The entire contents of each ofthe above applications are hereby incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to systems and methods for optimizingemissions from simultaneous activation of electrosurgery generators.

2. Background of Related Art

Electrosurgical generators are employed by surgeons in conjunction withan electrosurgical instrument to cut, coagulate, desiccate and/or sealpatient tissue. High frequency electrical energy, e.g., radio frequency(RF) energy, is produced by the electrosurgical generator and applied tothe tissue by an electrosurgical tool. Both monopolar and bipolarconfigurations are commonly used during electrosurgical procedures.

The electrical energy usually has its waveform shaped to enhance itsability to cut, coagulate or seal tissue. Different waveforms correspondto different modes of operation of the generator, and each mode givesthe surgeon various operating advantages. Modes may include, but are notlimited to, cut, coagulate, blend, desiccate, or spray. A surgeon mayeasily select and change the different modes of operation as thesurgical procedure progresses.

In each mode of operation, the electrosurgical power delivered to thepatient is regulated to achieve suitable surgical effect. Applying moreelectrosurgical power than necessary results in tissue destruction andprolongs healing. Applying less than the suitable amount ofelectrosurgical power inhibits the surgical procedure.

Electrosurgical techniques and instruments can be used to coagulatesmall diameter blood vessels or to seal large diameter vessels ortissue, e.g., veins and/or soft tissue structures, such as lung, andintestine. A surgeon can cauterize, coagulate/desiccate and/or simplyreduce or slow bleeding, by controlling the intensity, frequency andduration of the electrosurgical energy applied between the electrodesand through the tissue. For the purposes herein, the term“cauterization” is defined as the use of heat to destroy tissue (alsocalled “diathermy” or “electro-diathermy”). The term “coagulation” isdefined as a process of desiccating tissue wherein the tissue cells areruptured and dried.

“Vessel sealing” or “tissue fusion” is defined as the process ofliquefying the collagen and elastin in the tissue so that it reformsinto a fused mass with significantly-reduced demarcation between theopposing tissue structures (opposing walls of the lumen). Coagulation ofsmall vessels is usually sufficient to permanently close them whilelarger vessels or tissue need to be sealed to assure permanent closure.It has been known that different waveforms of electro surgical energyare suited for different surgical affects, e.g., cutting, coagulation,sealing, blend, etc. For example, the “cutting” mode typically entailsgenerating a continuous sinusoidal waveform in the frequency range of250 kHz to 4 MHz with a crest factor in the range of 1.4 to 2.0. The“blend” mode typically entails generating a periodic burst waveform witha duty cycle in the range of 25% to 75% and a crest factor in the rangeof 2.0 to 5.0. The “coagulate” mode typically entails generating aperiodic burst waveform with a duty cycle of approximately 10% or lessand a crest factor in the range of 5.0 to 12.0.

In order to optimize sealing or tissue fusion without causing unwantedcharring of tissue at the surgical site or possibly causing collateraldamage to adjacent tissue, e.g., thermal spread, it is necessary toaccurately control the output from the electrosurgical generator, e.g.,power, waveform, voltage, current, pulse rate, etc. It follows thataccurate measurement of the output power of an electrosurgical generatorgreatly benefits the design, manufacture, and use thereof. Thus, thereis continual need to improve delivery of energy to the tissue.

SUMMARY

In accordance with aspects of the present disclosure, a method ofperforming an electrosurgical procedure is presented. The methodincludes the steps of delivering first energy to a first target tissuevia a first generator, the first energy represented as a first waveformhaving a first phase, delivering second energy to a second target tissuevia a second generator, the second energy represented as a secondwaveform having a second phase, applying the first energy in a firstenergy mode in a predetermined time period, and applying the secondenergy in a second energy mode in the predetermined time period. Themethod also includes the steps of comparing the first phase of the firstenergy waveform with the second phase of the second energy waveform inone or more of the plurality of sub-periods, and adjusting a relativephase between the first and second energy waveforms based on thecomparison step.

According to an aspect of the present disclosure, the adjusting stepinvolves offsetting the first phase from the second phase by apredetermined amount.

According to a further aspect of the present disclosure, the offsettingresults in destructive interference of the first and second energywaveforms. Alternatively, the offsetting involves constructiveinterference of the first and second energy waveforms.

According to a further aspect of the present disclosure, the firstgenerator is coupled to a first micro-catheter and the second generatoris coupled to a second micro-catheter. The first micro-catheter appliesthe first energy to the first target tissue and the secondmicro-catheter applies the second energy to the second target tissue.

According to another aspect of the present disclosure, a modularelectrosurgical generator platform is presented. The modularelectrosurgical generator platform includes a first energy moduleconfigured to receive the power input and convert the power input into afirst energy, and to deliver the first energy represented as a firstwaveform having a first phase in a first energy mode, and a secondenergy module configured to receive the power input and convert thepower input into a second energy, and to deliver the second energyrepresented as a second waveform having a second phase in a secondenergy mode. The modular electrosurgical generator platform furtherincludes a host controller module configured to control a type and anumber of energy modalities provided by the generator platform. Themodular electrosurgical generator platform further includes a comparatorfor comparing the first phase of the first energy waveform with thesecond phase of the second energy waveform in one or more of theplurality of sub-periods and an adjustment module for adjusting arelative phase between the first and second generators based on resultsobtained from the comparator.

In accordance with aspects of the present disclosure, a method ofperforming an electrosurgical procedure is presented. The methodincludes the steps of delivering first energy represented as a firstwaveform via a first surgical instrument to a first target tissue,delivering second energy represented as a second waveform via a secondsurgical instrument to a second target tissue, comparing the firstwaveform to the second waveform, and adjusting a relative phase of thefirst and second waveforms to offset constructive interference.

In one aspect, the first energy mode is a cutting mode and the secondenergy mode is a coagulation mode. In another aspect, the first energymode is a coagulation mode and the second energy mode is a blend mode.In a further aspect, the first energy mode is a blend mode and thesecond energy mode is a division with hemostasis mode. In yet anotheraspect, the first energy mode is a division with hemostasis mode and thesecond energy mode is a fulguration mode. In another aspect, the firstenergy mode is a fulguration mode and the second energy mode is a spraymode. In yet another aspect, the first energy mode is a spray mode andthe second energy mode is a cutting mode. In yet another aspect, thefirst energy mode is a continuous energy mode and the second energy modeis a discontinuous energy mode.

In accordance with aspects of the present disclosure, a non-transitorycomputer-readable storage medium is presented for storingcomputer-executable instructions which, when executed by a computer,cause the computer to function as an information processing apparatusfor a modular electrosurgical generator platform, including a powersupply module configured to provide a power input, a first energy moduleconfigured to receive the power input and convert the power input into afirst energy, and to deliver the first energy represented as a firstwaveform having a first phase in a first energy mode, a second energymodule configured to receive the power input and convert the power inputinto a second energy, and to deliver the second energy represented as asecond waveform having a second phase in a second energy mode, a hostcontroller module configured to control a type and a number of energymodalities provided by the generator platform, a comparator forcomparing the first phase of the first energy waveform with the secondphase of the second energy waveform in one or more of a plurality ofsub-periods, and an adjustment module for adjusting a relative phasebetween the first and second generators based on results obtained fromthe comparator.

In one aspect, the adjustment module offsets the first phase from thesecond phase by a predetermined amount.

In another aspect, the offsetting results in destructive interference ofthe first and second energy waveforms.

In yet another aspect, the offsetting results in constructiveinterference of the first and second energy waveforms.

In one aspect, the energy modality is selected from the group consistingof cutting, coagulation, blend, division with hemostasis, fulguration,spray, and combinations thereof.

In another aspect, the first and second energy modules include an RFstage, a sensor stage, a controller stage, and a connector module stage.

In yet another aspect, the RF stage includes an inverter and a preamp.

In one aspect, the modular electrosurgical generator platform supportssimultaneous activation of two energy modes.

In another aspect, the host controller module manages requests andcontrols activation of energy types.

In yet another aspect, the relative phase is adjusted at predefinedfrequencies.

In accordance with aspects of the present disclosure, a non-transitorycomputer-readable storage medium is presented for storing acomputer-executable program of instructions for causing a computer toperform a method including delivering first energy to a first targettissue via a first generator, the first energy represented as a firstwaveform having a first phase, delivering second energy to a secondtarget tissue via a second generator, the second energy represented as asecond waveform having a second phase, applying the first energy in afirst energy mode in a predetermined time period, applying the secondenergy in a second energy mode in the predetermined time period,comparing the first phase of the first energy waveform with the secondphase of the second energy waveform in one or more of a plurality ofsub-periods, and adjusting a relative phase between the first and secondenergy waveforms based on the comparison step.

In one aspect, the adjusting step involves offsetting the first phasefrom the second phase by a predetermined amount.

In another aspect, the offsetting results in destructive interference ofthe first and second energy waveforms.

In yet another aspect, the offsetting results in constructiveinterference of the first and second energy waveforms.

In one aspect, the energy modes are at least one of: bipolar, monopolar,continuous, and discontinuous modes.

In another aspect, at least one modality is selected from the groupconsisting of cutting, coagulation, blend, division with hemostasis,fulguration, spray, and combinations thereof.

In accordance with aspects of the present disclosure, a non-transitorycomputer-readable storage medium is presented for storing acomputer-executable program of instructions for causing a computer toperform a method including delivering first energy represented as afirst waveform via a first surgical instrument to a first target tissue,delivering second energy represented as a second waveform via a secondsurgical instrument to a second target tissue, comparing the firstwaveform to the second waveform, and adjusting a relative phase of thefirst and second waveforms to offset constructive interference.

In one aspect, the comparing step involves comparing zero crossings ofthe first waveform with zero-crossings of the second waveform todetermine the relative phase between the first and second waveforms.

In another aspect, the comparing step involves performing sampling ofthe first and second waveforms in regions surrounding the zero crossingsof the first and second waveforms.

In yet another aspect, sampling data surrounding the zero crossings ofthe first and second waveforms is provided to a software algorithm forcomputing the relative phase between the first and second waveforms.

Further scope of applicability of the present disclosure will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating illustrative embodiments of the presentdisclosure, are given by way of illustration only, since various changesand modifications within the spirit and scope of the present disclosurewill become apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject systems and methods are describedherein with reference to the drawings wherein:

FIG. 1 is a schematic block diagram of a modular electrosurgicalgenerator platform, in accordance with embodiments of the presentdisclosure;

FIG. 2 is a schematic block diagram of a power supply module includingtwo generators, in accordance with an embodiment of the presentdisclosure;

FIG. 3 is a schematic block diagram of an energy module, in accordancewith an embodiment of the present disclosure;

FIG. 4 is a block diagram of a plurality of energy modules connected toa host module, in accordance with an embodiment of the presentdisclosure;

FIG. 5 illustrates an electrosurgical generator connected to twomicro-catheters to be inserted into a patient, in accordance with anembodiment of the present disclosure;

FIG. 6 is a flowchart illustrating a method of executing a calibrationprocedure, in accordance with an embodiment of the present disclosure;

FIGS. 7A-7C are waveforms illustrating constructive interference,according to one aspect of the present disclosure;

FIGS. 8A-8C are waveforms illustrating partial constructiveinterference, according to one aspect of the present disclosure;

FIGS. 8D-8F are waveforms illustrating complete destructive interference(i.e., 180° out-of-phase between waveforms), according to one aspect ofthe present disclosure;

FIGS. 9A-9C are blend mode waveforms illustrating constructiveinterference, according to one aspect of the present disclosure;

FIGS. 10A-10C are blend mode waveforms illustrating partial constructiveinterference, according to one aspect of the present disclosure;

FIGS. 10D-10F are waveforms illustrating no constructive interferenceaccording to one aspect of the present disclosure;

FIGS. 11A-11C are coag-driven waveforms, illustrating constructiveinterference, according to one aspect of the present disclosure;

FIGS. 12A-12C are coag-driven waveforms, which provide dissection withhemostasis, illustrating partial or incomplete destructive interference,according to one aspect of the present disclosure;

FIGS. 12D-12F are waveforms illustrating no constructive interferenceaccording to one aspect of the present disclosure;

FIGS. 13A-13C are two waveforms of different modalities illustratingconstructive interference, according to one aspect of the presentdisclosure;

FIGS. 14A-14C are two waveforms of different modalities illustratingpartial or incomplete destructive interference, according to one aspectof the present disclosure;

FIGS. 14D-14F are waveforms illustrating no constructive interferenceaccording to one aspect of the present disclosure;

FIG. 15A is a graphical representation illustrating sampling used todetermine a relative phase between two waveforms that are out-of-phaseby less than 180°, according to one aspect of the present disclosure;and

FIG. 15B is a graphical representation illustrating sampling used todetermine a relative phase between two waveforms that are out-of-phaseby 180°, according to one aspect of the present disclosure.

The figures depict preferred embodiments of the present disclosure forpurposes of illustration only. One skilled in the art will readilyrecognize from the following detailed description that alternativeembodiments of the structures and methods illustrated herein may beemployed without departing from the principles of the presentdisclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure. While certain embodiments of the present disclosure will bedescribed, it will be understood that it is not intended to limit theembodiments of the present disclosure to those described embodiments. Tothe contrary, it will be readily apparent to those skilled in this artthat various modifications, rearrangements and substitutions may be madewithout departing from the spirit of the present disclosure. Further,reference to embodiments of the present disclosure is intended to coveralternatives, modifications, and equivalents as may be included withinthe spirit and scope of the embodiments of the present disclosure asdefined by the appended claims.

Referring to FIG. 1, a high-level modular electrosurgical generatorplatform 100 is presented. The electrosurgical generator platform 100may include a power supply module 110, an energy module 120, a hostcontroller module 130, a backplane 140, and peripherals 150.

The power supply module 110 powers the energy module 120 with a requiredpower level. The energy module 120 takes input from the power supplymodule 110 and converts it into therapeutic energy at a frequencybetween, for example, 400-500 kHz. The backplane 140 may be a fixedcircuit board module that receives all sub-modules and carries allsignals between sub-modules. The backplane 140 communicates with thehost controller module 130 to facilitate with management of thesub-modules. The peripherals 150 may be, for example, footswitches.

Referring to FIG. 2, an electrosurgical system 200 may include a firstgenerator 210, a second generator 220, a selecting module 230, acomparator 240, and an adjustment module 250.

Referring to FIG. 3, the energy module 120 may include four differentstages. The first stage may be an RF stage 310, the second stage may bea sensor stage 320, the third stage may be a controller stage 330, andthe fourth stage may be a connector module stage 340.

The RF stage 310 includes a waveform generator 311, an inverter 312, anda preamp 314. The sensor stage 320 is used to monitor voltage fusingvoltage sensor 324) and current fusing current sensor 322) beingdelivered to a patient. The controller stage 330 reads the data fromsensors 322 and 324, processes the data, and modifies the settings ofthe RF stage 310 to adjust the power level based on predefined powercurves. The connector module stage 340 includes a receptacle allowingconnection to compatible instrument plugs. The connector stage module340 may include, but is not limited to, a barcode scanner to be used forinstrument recognition or RFID for the same purpose, as well as a meansfor insertion detection to determine if an instrument has been fullyinserted. Of course, one skilled in the art may contemplate any type ofmeans for instrument recognition. None of the exemplary embodimentsdescribed herein are limited to barcodes or RFID recognition.

Referring to FIG. 4, a plurality of energy modules 120 are connected tothe host controller module 130. The system 400 may support simultaneousactivation of two energy modules 120. It is contemplated that the system400 may support more than two energy modules 120. The host controllermodule 130 controls managing the request for energy and the activationof the energy, thus controlling which modules may be simultaneouslyactivated. Each energy module 120 communicates with the host controllermodule 130 via, for example, a PCI_(e) bus 135. The PCI_(e) bus may beselected based on its high speed, low latency, and availability with aplurality of central processing units (CPUs). The energy modules 120 maybe connected to a surgical instrument 410.

The host controller module 130 determines the type and number of energymodalities installed in the system, communicates with the energy modules120, and notifies the energy modules 120 when to provide energy uponreceiving an activation request and limits the number of energy modulesthat can be simultaneously activated. Additionally, the host controllermodule 130 controls the error handling and communication to the uservia, for example, a graphical user interface (GUI) (not shown). The hostcontroller module 130 may also communicate with a hospital network via,for example, a wireless connection. Further, the host controller 130 mayalso be responsible for managing data storage.

Additionally, the waveform generator 311 is configured to supply PWMsignals to the RF inverter 312. The output of RF inverter 312 may bemeasured by current sensor 322 and voltage sensor 324, which may bebilaterally coupled to an Energy Module Controller (FPGA) of energymodule 120.

Referring to FIG. 5, a system 500 includes electrosurgical generators210, 220 connected to two surgical instruments 530, 540 (e.g., first andsecond micro-catheters). The electrosurgical instruments 530, 540 areused during a surgical procedure performed on a patient 520 laying on atable 510 in an operating room. The two electrosurgical instruments 530,540 may be operated in the same energy modality. However, it iscontemplated that the two electrosurgical instruments 530, 540 may alsobe operated in different modalities. As illustrated in the system 500,during certain surgical procedures, simultaneous intervention at twodifferent sites may be required. Thus, the system 500 has dual channelsimultaneous activation capability.

Referring to FIG. 6, a flowchart 600 illustrating a method of executinga calibration procedure is presented.

The flowchart 600 includes the following steps. In step 610, acalibration procedure is commenced. In step 620, the next simultaneousmodality combination is activated. In step 630, the energy emission ismeasured and an ideal lag time for this modality combination iscalculated. The energy emission may be V, I, EM field, E or H field, ornear-field zone. In step 640, a time lag is applied to the waveform ofthe second channel by, for example, one sub-period. In step 650, it isdetermined whether all sub-periods are covered and are back in sync. IfNO, the process proceeds to step 630. If YES, the process proceeds tostep 660. In step 660, it is determined whether all the simultaneousmodality combinations are covered. If NO, the process proceeds to step620. If YES, the process proceeds to step 670, where the calibrationprocedure ends. The process then ends for the first cycle or firstiteration. However, the process may be a continuous iterative process.In other words, the steps of the process may repeat for a number cyclesor iterations, where the steps are constantly repeated.

Additionally, it is noted that the calibration procedure may occur atthe generator after the two devices 530, 540 are plugged in.Alternatively, the calibration procedure may occur by the manufacturerand be stored in the memory of the generators 210, 220 (or first andsecond energy modules).

With respect to FIGS. 7A-14F, it is shown how one channel is lagged intime with respect to another channel to provide emissive energyreduction at certain frequencies. The amount of time lag may be analogor digitally determined. In the digital domain, each waveform period orrepetition cycle is divided into an integer number of sub-periods, whichrepresent a finite length of time. The start of the waveform for thefirst channel may be lagged by starting the waveform of the secondchannel at “n,” sub-periods later, thus providing a time lag to reduceemissions. A calibration procedure may be developed to “tune” thesimultaneous activation by adjusting the time lag between thesimultaneous activation waveforms (see FIG. 6 described above).

Moreover, it is noted that the second waveform of the second channel maybe delayed for a period of time (e.g., medically insignificant period oftime) with respect to the first waveform of the first channel to allowfor optimum destructive interference (see FIGS. 7A-14F below). Optimumdestructive interference occurs when the first and second waveforms areout-of phase relative to each other by 180°.

Referring to FIGS. 7A-7C, waveforms illustrating constructiveinterference are presented. FIG. 7A shows the first channel 700Aillustrating a SINE wave 710, whereas FIG. 7B shows the second channel700B illustrating a SINE wave 720. The SINE wave 710 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The SINE wave 720 represents a second energy delivered to asecond target tissue via a second generator 220 (see FIG. 5).

It is noted that the first generator 210 may be a first energy moduleand the second generator 220 may be a second energy module. In otherwords, the first and second energy modules may be generators,themselves, that draw power from the common backplane 140 (see FIG. 1).Therefore, the term “generator” may be interchangeable with the term“energy module” for certain exemplary embodiments.

FIG. 7C illustrates a waveform resulting from the addition 700C ofwaveforms 710, 720. As shown, the first waveform 710 has an amplitude of2V and the second waveform 720 has an amplitude of 2V. The resultingwaveform 730 has an amplitude of 4V. In other words, when both surgicalinstruments 530, 540 (see FIG. 5) are simultaneously used on a patient520 and the waveforms 710, 720 are in-phase with respect to each other,the energy at all the frequencies is additive, which results inconstructive interference.

Interference is a phenomenon in which two waves superimpose to form aresultant wave of greater or lower amplitude. Interference refers to theinteraction of waves that are correlated or coherent with each other,either because they come from the same source or because they have thesame or nearly the same frequency. The principle of superposition ofwaves states that when two or more propagating waves of like type areincident on the same point, the total displacement at that point isequal to the vector sum of the displacements of the individual waves. Ifa crest of a wave coincides with a crest of another wave (i.e., inphase) of the same frequency at the same point, then the magnitude ofthe displacement is the sum of the individual magnitudes. This isreferred to as constructive interference. If a crest of one wavecoincides with a trough of another wave (i.e., out of phase) then themagnitude of the displacements is equal to the difference in theindividual magnitudes. This is known as destructive interference (seeFIGS. 8A-8B below). If the difference between the phases is intermediatebetween these two extremes, then the magnitude of the displacement ofthe summed waves lies between the minimum and maximum values.

Thus, in the exemplary embodiments of the present disclosure, therelative phases (between the waveforms) of the respective simultaneouschannels are varied such that the emission based additive nature (orconstructive interference) of the energy at harmonics is minimized. Theterm “phase,” as used herein, is relative to something else. Forexample, the term “phase” is used relative to another “waveform,” asdescribed relative to FIGS. 7A-14F.

Stated differently, the system of the present disclosure maximizes thedestructive interference or keeps the constructive interference withinsome predetermined maximum value(s). This is applicable to all modes, aswell as to a mixture of modes (see FIGS. 13A-14F). The sub-period may bethe least common denominator of all of the modes. A software program maybe programmed to command the relative phase between the simultaneouswaveforms in number of sub-periods to provide emissive energy reductionat certain frequencies. A change in phase (e.g., an optimal time shift)between two waveforms provides different constructive interference anddestructive interference effects. The software may include a harmonicminimizer algorithm.

Referring to FIGS. 8A-8C, waveforms illustrating partial constructiveinterference are presented. FIG. 8A shows the first channel 800Aillustrating a SINE wave 810, whereas FIG. 7B shows the second channel800B illustrating a SINE wave 820. The SINE wave 810 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The SINE wave 820 represents a second energy delivered to asecond target tissue via a second generator 220 (see FIG. 5). FIG. 8Cillustrates a waveform resulting from the addition 800C of waveforms810, 820. As shown, the first waveform 810 has an amplitude of 2V andthe second waveform 820 has an amplitude of 2V. However, the resultingwaveform 830 does not have an amplitude of 4V at every crest or peak. Inother words, when both surgical instruments 530, 540 (see FIG. 5) aresimultaneously used on a patient 520 and the waveforms 810, 820 areout-of-phase (or out of sync) with respect to each other by a timedistance shown as 822 in FIG. 8B, the energy at some of the frequenciesis additive, whereas the energy at some of the frequencies issubtractive, thus resulting in partial constructive/destructiveinterference at select points.

For example, wave portion 835 illustrates the additive nature of thewaveforms 810, 820, whereas wave portion 837 illustrates the subtractivenature of the waveforms 810, 820. When both surgical instruments 530,540 (see FIG. 5) are simultaneously used on a patient 520, it is desiredto create as much destructive interference of the waveforms 810, 820 aspossible. In order to accomplish this, a first energy is applied in afirst energy mode at a predetermined time period and a second energy isapplied in a second energy mode at the predetermined time period. Aplurality of sub-periods may then be selected in that predetermined timeperiod. Then a first phase of the first waveform 810 is compared to asecond phase of the second waveform 820 in one or more of the pluralityof predetermined sub-periods. A relative phase between the waveforms ofthe first and second generators 210, 220 (or first and second energymodules) is then adjusted based on the comparison step in order tocreate more destructive interference. The adjusting step involvesoffsetting the first phase from the second phase (between waveforms) bya predetermined amount to produce different destructive interferenceeffects based on the selected modes of operation of each surgicalinstrument 530, 540. The relative phase between waveforms may also beadjusted at certain predefined frequencies. The relative phase betweenwaveforms is varied by software to optimize a time shift. The waveformis shifted by a carrier frequency. The source of the carrier frequencyis a set of PWM signals that are sent into the RF inverter component forFET switching. The set of PWM signals are time-shifted by a specifiedsub-period amount.

FIGS. 8D-8F are waveforms illustrating complete destructive interference(i.e., 180° out-of-phase between waveforms), according to one aspect ofthe present disclosure.

FIG. 8D shows a first channel 800D illustrating a first waveform 840,whereas FIG. 8E shows a second channel 800E illustrating a secondwaveform 850 that is out-of-phase with the first waveform 840 by 180°.FIG. 8F illustrates a waveform resulting from the addition of first andsecond waveforms 840, 850. Waveform 860 illustrates complete destructiveinterference that results from the additions of waveforms 840, 850. As aresult, waveform 860 has an amplitude of 0° and extends along thex-axis. In other words, when both surgical instruments 530, 540 (seeFIG. 5) are simultaneously used on a patient 520 and the waveforms 840,850 are out-of-phase by a time distance shown as 855 in FIG. 8E, theenergy at all of the frequencies is subtractive, thus resulting incomplete destructive interference.

One objective of the partial or complete destructive interference is tolower the E field or the H field or the EM field to the surgeon orpatient or support staff near the surgical site. Additionally, all thewaveforms illustrated in FIGS. 8A-8F may be representative of voltage(V) or current (I) or radiated RF (V/m, A/m or power density, such asmW/cm²).

Referring to FIGS. 9A-9B, waveforms illustrating constructiveinterference are presented for a blend mode. FIG. 9A shows the firstchannel 900A illustrating a wave 910, whereas FIG. 9B shows the secondchannel 900B illustrating a wave 920. The wave 910 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The wave 920 represents a second energy delivered to a secondtarget tissue via a second generator 220 (see FIG. 5). FIG. 9Cillustrates a waveform resulting from the addition 900C of waveforms910, 920. As shown, the first waveform 910 has an amplitude of 2V andthe second waveform 920 has an amplitude of 2V. The resulting waveform930 has an amplitude of 4V. In other words, when both surgicalinstruments 530, 540 (see FIG. 5) are simultaneously used on a patient520 and the waveforms 910, 920 are in-phase, the energy at all thefrequencies is additive, which results in constructive interference.This situation is desired to be avoided by providing at least onewaveform out-of-phase (or out of sync) with respect to the otherwaveform, as shown in FIGS. 10A-10C.

Referring to FIGS. 10A-10C, waveforms illustrating partial constructiveinterference are presented. FIG. 10A shows the first channel 1000Aillustrating a wave 1010, whereas FIG. 10B shows the second channel1000B illustrating a wave 1020. The wave 1010 represents a first energydelivered to a first target tissue via a first generator 210 (see FIG.5). The wave 1020 represents a second energy delivered to a secondtarget tissue via a second generator 220 (see FIG. 5). FIG. 10Cillustrates a waveform resulting from the addition 1000C of waveforms1010, 1020. As shown, the first waveform 1010 has an amplitude of 2V andthe second waveform 1020 has an amplitude of 2V. However, the resultingwaveform 1030 does not have an amplitude of 4V at every crest or peak.In other words, when both surgical instruments 530, 540 (see FIG. 5) aresimultaneously used on a patient 520 and the waveforms 1010, 1020 areout-of-phase (or out of sync) by a distance shown as 1022 in FIG. 10B,the energy at some of the frequencies is additive, whereas the energy atsome of the frequencies is subtractive, thus resulting in at least someconstructive/destructive interference at certain points.

For example, wave portion 1035 illustrates the additive nature of thewaveforms 1010, 1020, whereas wave portion 1037 illustrates thesubtractive nature of the waveforms 1010, 1020. When both surgicalinstruments 530, 540 (see FIG. 5) are simultaneously used on a patient520, it is desired to create as much destructive interference of thewaveforms 1010, 1020 as possible, in order to simultaneously operateboth surgical instruments 530, 540 in a blend mode. In order toaccomplish this, a first energy is applied in a first energy mode at apredetermined time period and a second energy is applied in a secondenergy mode at the predetermined time period, where the first and secondenergy modes are the same. A plurality of sub-periods may then beselected in that predetermined time period. Then a first phase of thefirst waveform 1010 is compared to a second phase of the second waveform1020 in one or more of the plurality of predetermined sub-periods. Arelative phase between the first and second generators 210, 220 (orenergy modules) is then adjusted based on the comparison step in orderto create more destructive interference. The adjusting step involvesoffsetting the first phase from the second phase by a predeterminedamount to produce different destructive interference effects based onthe selected modes of operation of each surgical instrument 530, 540.The relative phase may also be adjusted at certain predefinedfrequencies.

FIGS. 10D-10F are waveforms illustrating no constructive interference,according to one aspect of the present disclosure.

FIG. 10D shows a first channel 1000D illustrating a first waveform 1040,whereas FIG. 10E shows a second channel 1000E illustrating a secondwaveform 1050 that is out-of-phase with the first waveform 1040 by 180°.FIG. 10F illustrates a waveform resulting from the addition 1000F offirst and second waveforms 1040, 1050. Waveform 1060 illustrates noconstructive interference that results from the additions of waveforms1040, 1050. As a result, waveform 1060 has an amplitude of 0° andextends along the x-axis. In other words, when both surgical instruments530, 540 (see FIG. 5) are simultaneously used on a patient 520 and thewaveforms 1040, 1050 are out-of-phase by a time distance shown as 1055in FIG. 10E, and the energy at all frequencies results in noconstructive interference.

One objective of the partial or complete destructive interference is tolower the E field or the H field or the EM field to the surgeon orpatient or support staff near the surgical site. Additionally, all thewaveforms illustrated in FIGS. 10A-10F may be representative of voltage(V) or current (I) or radiated RF (V/m, A/m or power density, such asmW/cm²).

Referring to FIGS. 11A-11B, waveforms illustrating constructiveinterference are presented for a coag-driven mode. FIG. 11A shows thefirst channel 1100A illustrating a wave 1110, whereas FIG. 11B shows thesecond channel 1100B illustrating a wave 1120. The wave 1110 representsa first energy delivered to a first target tissue via a first generator210 (see FIG. 5). The wave 1120 represents a second energy delivered toa second target tissue via a second generator 220 (see FIG. 5). FIG. 11Cillustrates a waveform resulting from the addition 1100C of waveforms1110, 1120. As shown, the first waveform 1110 has an amplitude of 2V andthe second waveform 1120 has an amplitude of 2V. The resulting waveform1130 has an amplitude of 4V. In other words, when both surgicalinstruments 530, 540 (see FIG. 5) are simultaneously used on a patient520 and the waveforms 1110, 1120 are in-phase, the energy at all thefrequencies is additive, which results in constructive interference.This situation is desired to be avoided by providing at least onewaveform out-of-phase (or out of sync) with respect to the otherwaveform, as shown in FIGS. 12A-12C.

Referring to FIGS. 12A-12C, waveforms illustrating partial or incompletedestructive interference are presented. FIG. 12A shows the first channel1200A illustrating a wave 1210, whereas FIG. 12B shows the secondchannel 1200B illustrating a wave 1220. The wave 1210 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The wave 1220 represents a second energy delivered to a secondtarget tissue via a second generator 220 (see FIG. 5). FIG. 12Cillustrates a waveform resulting from the addition 1200C of waveforms1210, 1220. As shown, the first waveform 1210 has an amplitude of 2V andthe second waveform 1220 has an amplitude of 2V. However, the resultingwaveform 1230 does not have an amplitude of 4V at every crest or peak.In other words, when both surgical instruments 530, 540 (see FIG. 5) aresimultaneously used on a patient 520 and the waveforms 1210, 1220 areout-of-phase (or out of sync), such that the energy at all thefrequencies is subtractive, thus resulting in partial destructiveinterference.

For example, waveform 1210 includes three SINE wave portions 1, 2, 3,whereas waveform 1220 includes four SINE wave portions 4, 5, 6, 7. TheSINE wave portions 1, 2, 3 are out-of-phase (or out of sync) withrespect to the four SINE wave portions 4, 5, 6, 7. Therefore, in FIG.12C, when waveforms 1210, 1200 are added, there is no constructiveinterference and the peaks or crests of all the SINE wave portions 1-7are maintained within a band or region that is less than 2V.

FIGS. 12D-12F are waveforms illustrating no constructive interference,according to one aspect of the present disclosure.

FIG. 12D shows a first channel 1200D illustrating a first waveform 1240,whereas FIG. 12E shows a second channel 1200E illustrating a secondwaveform 1250 that is out-of-phase with the first waveform 1240 by 180°.FIG. 12F illustrates a waveform resulting from the addition 1200F offirst and second waveforms 1240, 1250. Waveform 1260 illustrates noconstructive interference that results from the additions of waveforms1240, 1250. As a result, waveform 1260 has an amplitude of 0° andextends along the x-axis. In other words, when both surgical instruments530, 540 (see FIG. 5) are simultaneously used on a patient 520 and thewaveforms 1240, 1250 are out-of-phase by 180°, and the energy at allfrequencies results in no constructive interference.

One objective of the partial or complete destructive interference is tolower the E field or the H field or the EM field to the surgeon orpatient or support staff near the surgical site. Additionally, all thewaveforms illustrated in FIGS. 12A-12F may be representative of voltage(V) or current (I) or radiated RF (V/m, A/m or power density, such asmW/cm²).

Referring to FIGS. 13A-13B, waveforms illustrating constructiveinterference are presented for a mixed mode of operation. FIG. 13A showsthe first channel 1300A illustrating a wave 1310 operating in a blendmode, whereas FIG. 13B shows the second channel 1300B illustrating awave 1320 operating in a coag-driven. The wave 1310 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The wave 1320 represents a second energy delivered to a secondtarget tissue via a second generator 220 (see FIG. 5). FIG. 13Cillustrates a waveform resulting from the addition 1300C of waveforms1310, 1320. As shown, the first waveform 1310 has an amplitude of 2V andthe second waveform 1320 has an amplitude of 2V. The resulting waveform1330 has an amplitude of 4V. In other words, when both surgicalinstruments 530, 540 (see FIG. 5) are simultaneously used on a patient520 and the waveforms 1310, 1320 are in-phase, the energy at certainfrequencies is additive, which results in constructive interference.This situation is desired to be avoided by providing at least onewaveform out-of-phase (or out of sync) with respect to the otherwaveform, as shown in FIGS. 14A-14C.

Referring to FIGS. 14A-14C, waveforms illustrating partial or incompletedestructive interference are presented. FIG. 14A shows the first channel1400A illustrating a wave 1410, whereas FIG. 14B shows the secondchannel 1400B illustrating a wave 1420. The wave 1410 represents a firstenergy delivered to a first target tissue via a first generator 210 (seeFIG. 5). The wave 1420 represents a second energy delivered to a secondtarget tissue via a second generator 220 (see FIG. 5). FIG. 14Cillustrates a waveform resulting from the addition 1400C of waveforms1410, 1420 having different energy modes. As shown, the first waveform1410 has an amplitude of 2V and the second waveform 1420 has anamplitude of 2V. However, the resulting waveform 1430 does not have anamplitude of 4V at every crest or peak. In other words, when bothsurgical instruments 530, 540 (see FIG. 5) are simultaneously used on apatient 520 and the waveforms 1410, 1420 are out-of-phase (or out ofsync), the energy at some of the frequencies is additive, whereas theenergy at some of the frequencies is subtractive, thus resulting inpartial destructive interference.

For example, waveform 1410 includes three SINE wave portions 1, 2, 3,whereas waveform 1420 includes two SINE wave portions 4, 5. The SINEwave portions 1, 2, 3 are out-of-phase (or out of sync) with respect tothe two SINE wave portions 4, 5. Therefore, in FIG. 14C, when waveforms1410, 1420 are added, there is no constructive interference and thepeaks or crests of all the SINE wave portions 1-5 are maintained withina band or region that is less than 4V.

FIGS. 14D-14F are waveforms illustrating no constructive interference,according to one aspect of the present disclosure.

FIG. 14D shows a first channel 1400D illustrating a first waveform 1440,whereas FIG. 14E shows a second channel 1400E illustrating a secondwaveform 1450 that is out-of-phase with the first waveform 1440 by 180°.FIG. 14F illustrates a waveform resulting from the addition 1400F offirst and second waveforms 1440, 1450. Waveform 1460 illustrates noconstructive interference that results from the additions of waveforms1440, 1450. As a result, waveform 1460 has an amplitude of 0° andextends along the x-axis. In other words, when both surgical instruments530, 540 (see FIG. 5) are simultaneously used on a patient 520 and thewaveforms 1440, 1450 are out-of-phase by 180°, the energy at all of thefrequencies is subtractive, and the energy at all frequencies results inno constructive interference.

One objective of the partial or complete destructive interference is tolower the E field or the H field or the EM field to the surgeon orpatient or support staff near the surgical site. Additionally, all thewaveforms illustrated in FIGS. 14A-14F may be representative of voltage(V) or current (I) or radiated RF (V/m, A/m or power density, such asmW/cm²).

Therefore, with respect to FIGS. 7A-14F, based on how the softwareprogram is executed, constructive interference may reduced or completelyeliminated when two surgical instruments 530, 540 (e.g.,micro-catheters) are simultaneously used on different regions or targetsites of a patient 520. Of course, one skilled in the art maycontemplate using any type of surgical instruments. The term“micro-catheters” is merely used as an exemplary illustration for thereader. Thus, the term “surgical instruments” is not limited thereto.

Ideally, the two waveforms would be 180° degrees out-of-phase tocompletely eliminate constructive interference effects (see FIGS. 8D-8F,10D-10F, 12D-12F, and 14D-14F). The software program would command therelative phase between the two waveforms to be adjusted, continuouslyand in real-time, in a number of sub-periods to provide for emissiveenergy reduction at certain frequencies. As a result, reduced radiationexposures for surgeons, clinicians, and patients may be achieved, aswell as reduction in interference to other medical devices or equipmentin the vicinity of the surgical site. Thus, the human exposure issue isbeing addressed herein with respect to the exemplary embodiments of thepresent disclosure.

It is also contemplated that the energy emission of each surgicalinstrument may be continuously computed and displayed on a displayscreen, either in the operating room or remotely. Additionally, it iscontemplated that the combined energy emission may also be displayed ona display screen concurrently with the energy emission of each waveformin order to determine by how much the energy emission has been reduced.Thus, the actual energy reduction may be provided and displayed inreal-time.

Referring to FIG. 15A, an illustration of sampling 1500A two waveforms1502, 1504 are shown broken into a small number of samples that are usedto determine the phase shift to achieve suitable destructiveinterference effects. For example, a first waveform 1502 of a firstchannel has two zero crossings 1510. Sampling may occur directly beforeand directly after the zero crossing 1510. Samples 1512, 1514, 1516,1518 may be extracted from the first waveform 1502. Similarly, a secondwaveform 1504 of a second channel has two zero crossings 1520. Samplingmay occur directly before and directly after the zero crossing 1520.Samples 1522, 1524, 1526, 1528 may be extracted from the second waveform1504. The samples of the first and second waveforms 1502, 1504 near thezero crossings 1510, 1520 are analyzed and a relationship is developedtherebetween. This sampling data is provided to a software algorithm fordetermining the relative phase between the waveforms 1502, 1504. Ofcourse, this is merely an exemplary illustration of sampling that can beapplied to any types of waveforms created by the generators 210, 220(see FIG. 5).

Similar to FIG. 15A, FIG. 15B is an illustration of sampling 1500B twowaveforms 1502, 1504 that are shown broken into a small number ofsamples that are used to determine the phase shift to achieve suitabledestructive interference effects. In FIG. 15B, however, the waveforms1502, 1504 are shown to be 180° out-of-phase with respect to each other,as opposed to FIG. 15A, where the waveforms 1502, 1504 are shown to beless than 180° out-of-phase with respect to each other.

One skilled in the art may extract samples from any portion of thewaveforms (i.e., not necessarily near the zero crossings) in order toprovide sampling data to the software algorithm. Thus, the sampling datais used to determine the relative phase between the waveforms in orderto maintain the amplitude of the waveforms within a suitable oracceptable range. Moreover, sampling may occur at a very high rate, forexample, at over 20 million times per second. One skilled in the art mayuse any suitable sampling rate. The sampling may also occur within thegenerators 210, 220 or energy modules (see FIG. 5).

The illustrated devices or methods described above may be implemented insoftware, hardware, firmware or combinations thereof. The stepsdiscussed herein need not be performed in the stated order. Several ofthe steps could be performed concurrently with each other. Furthermore,if desired, one or more of the above described steps may be optional ormay be combined without departing from the scope of the presentdisclosure. Thus, the features and aspects of the present disclosure maybe implemented in any suitable fashion by using any suitable software,firmware, and/or hardware.

For instance, when implemented via executable instructions, variouselements of the present disclosure are in essence the code defining theoperations of such various elements. The executable instructions or codemay be obtained from a readable medium (e.g., a hard drive media,optical media, EPROM, EEPROM, tape media, cartridge media, flash memory,ROM, memory stick, and/or the like) or communicated via a data signalfrom a communication medium (e.g., the Internet). In fact, readablemedia may include any medium that may store or transfer information.

The computer means or computing means or processing means may beoperatively associated with the assembly, and is directed by software tocompare the first output signal with a first control image and thesecond output signal with a second control image. The software furtherdirects the computer to produce diagnostic output. Further, a means fortransmitting the diagnostic output to an operator of the verificationdevice is included. Thus, many applications of the present disclosurecould be formulated. The exemplary network disclosed herein may includeany system for exchanging data or transacting business, such as theInternet, an intranet, an extranet, WAN (wide area network), LAN (localarea network), satellite communications, and/or the like. It is notedthat the network may be implemented as other types of networks.

Additionally, “code” as used herein, or “program” as used herein, may beany plurality of binary values or any executable, interpreted orcompiled code which may be used by a computer or execution device toperform a task. This code or program may be written in any one ofseveral known computer languages. A “computer,” as used herein, may meanany device which stores, processes, routes, manipulates, or performslike operation on data. A “computer” may be incorporated within one ormore transponder recognition and collection systems or servers tooperate one or more processors to run the transponder recognitionalgorithms. Moreover, computer-executable instructions include, forexample, instructions and data which cause a general purpose computer,special purpose computer, or special purpose processing device toperform a certain function or group of functions. Computer-executableinstructions also include program modules that may be executed bycomputers in stand-alone or network environments. Generally, programmodules include routines, programs, objects, components, and datastructures, etc. that perform particular tasks or implement particularabstract data types.

It is noted that the energy modes are at least one of bipolar,monopolar, continuous, and discontinuous modes. It is further noted thatthe modality is selected from the group consisting of cutting,coagulation, blend, division with hemostasis, fulguration, spray, andcombinations thereof. Of course, one skilled in the art may contemplatea number of other energy modes and/or modalities based on differentdesired applications.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure. Thus,appearances of the phrases “one embodiment,” “an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment, different embodiments, orcomponent parts of the same or different illustrated disclosure.Additionally, reference to the wording “an embodiment,” or the like, fortwo or more features, elements, etc. does not mean that the features arerelated, dissimilar, the same, etc. The use of the term “an embodiment,”or similar wording, is merely a convenient phrase to indicate optionalfeatures, which may or may not be part of the present disclosure asclaimed. The independent embodiments are considered to be able to becombined in whole or in part one with another as the claims and/or artmay direct, either directly or indirectly, implicitly or explicitly.

Moreover, the fact that the wording “an embodiment,” or the like, doesnot appear at the beginning of every sentence in the specification, suchas is the practice of some practitioners, is merely a convenience forthe reader's clarity. However, it is the intention of this applicationto incorporate by reference the phrasing “an embodiment,” and the like,at the beginning of every sentence herein where logically possible andappropriate.

The foregoing examples illustrate various aspects of the presentdisclosure and practice of the methods of the present disclosure. Theexamples are not intended to provide an exhaustive description of themany different embodiments of the present disclosure. Thus, although theforegoing present disclosure has been described in some detail by way ofillustration and example for purposes of clarity and understanding,those of ordinary skill in the art will realize readily that manychanges and modifications may be made thereto without departing form thespirit or scope of the present disclosure.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

The invention claimed is:
 1. A method for optimizing emissions fromsimultaneous activation of first and second electrosurgical generators,the method comprising: delivering first energy to a first target tissuevia the first generator, the first energy represented as a firstwaveform having a first phase; delivering second energy to a secondtarget tissue via the second generator, the second energy represented asa second waveform having a second phase; applying the first energy in afirst energy mode in a predetermined time period; applying the secondenergy in a second energy mode in the predetermined time period;comparing the first phase of the first energy waveform with the secondphase of the second energy waveform in one or more of a plurality ofsub-periods; and adjusting a relative phase between the first and secondenergy waveforms based on the comparison step, the second waveform beingdelayed for a period of time to allow for optimum destructiveinterference.
 2. The method according to claim 1, wherein the firstgenerator is coupled to a first micro-catheter and the second generatoris coupled to a second micro-catheter.
 3. The method according to claim2, wherein the first micro-catheter applies the first energy to thefirst target tissue and the second micro-catheter applies the secondenergy to the second target tissue.
 4. The method according to claim 1,wherein the relative phase is adjusted at predefined frequencies.
 5. Themethod according to claim 1, wherein: the one or more of the pluralityof sub-period is two or more of the plurality of sub-periods; and thepredetermined amount is an integer multiple of sub-periods.
 6. Themethod according to claim 5, wherein: the comparing step comprisesidentifying a combined waveform of the first waveform and the secondwaveform having a lowest constructive interference among a plurality ofphase differentials between the first and second waveforms, the phasedifferentials being associated with an associated one of the pluralityof sub-periods; and the integer multiple of sub-periods being associatedwith the lowest constructive interference.
 7. The method according toclaim 1, wherein the first energy mode and the second energy mode are ofa different type.
 8. The method according to claim 1, wherein theadjusting step includes offsetting the first phase from the second phaseby a predetermined amount.
 9. A method for optimizing emissions fromsimultaneous activation of electrosurgery generators, the methodcomprising: delivering first energy represented as a first waveform viaa first surgical instrument to a first target tissue; delivering secondenergy represented as a second waveform via a second surgical instrumentto a second target tissue; comparing the first waveform to the secondwaveform; and adjusting a relative phase of the first and secondwaveforms to offset constructive interference, the adjusting stepincluding offsetting the first waveform from the second waveform by apredetermined amount, wherein the first energy is delivered via a firstenergy module and the second energy is delivered via a second energymodule, the first and second energy modules are configured to draw powerfrom a common backplane, and the second waveform is delayed for a periodof time to allow for optimum destructive interference.
 10. The methodaccording to claim 9, wherein the comparing step involves performingsampling of the first and second waveforms in regions surrounding thezero crossings of the first and second waveforms.
 11. The methodaccording to claim 10, wherein sampling data surrounding the zerocrossings of the first and second waveforms is provided to a softwarealgorithm for computing the relative phase between the first and secondwaveforms.
 12. The method according to claim 9, wherein the comparingstep including comparing zero crossings of the first waveform withzero-crossings of the second waveform to determine the relative phasebetween the first and second waveforms.